Caption: Nerve fibre node. Transmission electron micrograph (TEM) of a longitudinal section through a nerve fibre at a node of Ranvier, showing the nerve tissue (red) and the myelin sheath (dark blue). The myelin sheath is absent at a region known as a node of Ranvier (far left). Myelin is an insulating material that increases the speed of conduction of nerve impulses. The exposed areas at the nodes of Ranvier contain many sodium channels, allowing nerve impulses to start and propagate between these nodes, a process called saltatory conduction. This regenerates a nerve impulse, allowing it to travel over long distances. Magnification: x8000 when printed 10cm wide.